It is generally agreed that soluble carbohydrates are the most available, as well as the original, source of metabolic energy for plants. Hence, studies of the formation, translocation, condensation, hydrolysis and assimilation of these compounds have commanded, and will undoubtedly continue to command, a major place in plant physiological analysis. Separation between soluble and insoluble carbohydrates is here made by classing as insoluble those compounds which require hydrolysis before they can be quantitatively extracted from plant tissues by water or alcohol. In the strictest sense the extraction of dextrins and pentosans is probably accomplished by suspension rather than by true solution, but for analytical purposes they may be termed \"soluble\" compounds. In the interest of completeness we have included the glucosides under this heading, although it is hardly probable that they should be classed with the carbohydrates from the standpoint of physiological function. A brief treatment of the occurrence, solubility, reducing power and other properties of the carbohydrates here considered is given by HAAs and HILL (4). All but pectins and the gums are readily soluble in water. These and the polysaccharides (dextrin, inulin and mannan) are insoluble in hot 80 per cent. alcohol. It is well known that all naturally occurring free sugars with the exception of sucrose and raffinose seduce Fehling's solution. The saponins also have this property. Other glucosides, the soluble polysaccharides, pectins and gums acquire reducing power by hydrolysis, as do the non-reducing sugars. Furthermore, such reducing disaccharides as maltose and lactose acquire an increase of this property by hydrolysis. The latter carbohydrate is added to tissue in the use of commercial taka-diastase, which may contain up to 75 per cent. of the sugar. The presence of more than two or three per cent. of pentose sugars, or of appreciable quantities of galactose or mannose, is generally considered to be an indication of poor technique in preservation or separation, since these sugars are transition compounds normally present in polymerized forms. DAVIS and DAISH (2) are authority for the statement that the presence of maltose or isomaltose is due to starch hydrolysis in preservation and they object on this ground to preservation by drying. Apparently germinating seedlings may be an exception to this rule, but it is general enough in its application to be of value.

The Determination Of Soluble Carbohydrates

Determination of Dextrin, Maltose, and Dextrose in Corn Sirup

T he newer knowledge of nutrition shows that cereals and seed products are deficient in calcium, sodium, chlorine, and unknown substances, called fat-soluble A and water-soluble B sometimes referred to as “vitamines” or “accessory food factors.” McCollum(1) in America, has gone the length of proving bj actual experiment that cows and their calves can be raised to perfection on nothing but the complete maize plant, although maize grain is well known as a very incomplete food. In spite of his demonstration, and in spite of the obvious fact that nothing could be more like grass than an entire cereal plant and therefore suited to herbivora, very few practical or theoretical agriculturists recognise that straw is the most likely thing in the world to correct for the deficiencies of grain feeding. The difficulty is to get straw that is eatable. The practical farmer, when he happens to get a good sample, accepts it as a gift of fate and is content to turn it into profit for himself as soon as he can. The object of the enquiry, or rather the series of enquiries of which this forms a part, is to adopt the more scientific mode of procedure and endeavour to find out what differences of feeding value naturally occur in oat straw, and which of the conditions needed for high feeding value could be repeated at will, and what light such investigation threw on the old question of why farmers in some districts can fatten cattle on swedes and straw whilst in other districts it is found impossible. Oat straw is plentiful in this country and is probably well supplied with the so-called food accessories, that is the things that the grains lack; the problem at issue is how to get more of the eatable kind and less of the uneatable kind. Provided that the straw is eaten in fair quantity, the possible diminution of growth power, by partial destruction of vitamines due to keeping straw in the stack, is of no practical importance because of the large amount of the straw.

The sugars and albuminoids of oat straw

G. Cecil Jones

Papers

The estimation of iron by permanganate in presence of hydrochloric acid

The volumetric determination of reducing sugars. Part II.—The limits of accuracy of the method under standard conditions

Estimation of methyl alcohol in presence of ethyl alcohol